The Orofacial Pain Research Center will be a collaborative effort between researchers in the UCLA School of Dentistry and the UCLA School of Medicine. The Center will be based in the Dental Research Institute (DRI) at the UCLA School of Dentistry and will draw heavily upon the patients of the Temporomandibular and Facial Pain Clinic (TMFPC) in the School of Dentistry and the Pain Management Center (PMC) in the School of Medicine. The projects which involve human subjects will occur within the UCLA DRI's Clinical Research Center (CRC) whenever possible. This application contains five research projects that test a number of hypotheses around the central theme of orofacial pain research. One of these projects involve an animal model. This project is on herpes simplex virus and its effect on trigeminal nerve function in guinea pigs. Two other projects will involve research on the diagnosis, etiology or underlying mechanisms of various orofacial pain problems in human subjects. One is a study of the significance of temporomandibular tomograms in the diagnostic process for temporomandibular disorder patients. Another is an evaluation of masticatory muscle activity patterns (both ambulatory and sleeping) in patients diagnosed with chronic headaches. Finally, there are two studies on the treatment of orofacial pain problems. One is a study of the effectiveness of two commonly used medications (antidepressants and neuroleptics for the treatment of chronic post-herpetic neuralgia. The other is a study involving the assessment of various psychological factors as a method of predicting which TM disorder patients will improve with conventional physical medicine treatment. The second part of this study will involve the evaluation of patients who do not significantly improve with the above treatment regime. It will compare the effectiveness of two psychological treatments to a waiting list control group.